This invention relates to radio transceivers. In particular, it relates to a method and means of using a single high-stability frequency source to control transmission and to control a local oscillator upon receiving.
Most two-way radio communication is carried out using transceivers that transmit in one band of frequencies and receive in a different band of frequencies. An associated pair of frequency bands is often referred to as a channel. Thus, when a transceiver is operating in a particular channel, it must generate at least one frequency to transmit and at least one frequency with which to mix a received signal to produce a fixed intermediate frequency. The frequencies of transmission and reception may be the same but are usually different. As broadcast frequencies reach higher and higher bands, the need for stable oscillators increases the cost of transceivers, since the cost of oscillators increases rapidly as the allowable frequency deviation in parts per million is reduced. Since the stability of oscillators is a major factor in controlling interference between adjacent channels on transmitting and in maintaining selectivity on receiving, it has often been necessary in transceivers designed for VHF and higher frequencies, in the range of 150 MHz and above, to have two or more high-stability oscillators in a transceiver. This is a costly requirement. The use of a single high-stability oscillator would make it possible to produce a UHF transceiver at a lower cost.